Mainz 2012 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 64: Instrumentation
HK 64.5: Talk
Friday, March 23, 2012, 15:15–15:30, P 2
Performance Improvement of a Time-of-Flight detector and Longer Observation of Circulating Ions for IMS at FRS-ESR — •Marcel Diwisch1, Natalia Kuzminchuk1, Samuel Ayet2, Timo Dickel1,2, Hans Geissel1,2, Ronja Knöbel1,2, Wolfgang Plaß1,2, Christoph Scheidenberger1,2, Baohua Sun1,2, and Helmut Weick2 — 1Justus-Liebig-Universität Gießen — 2GSI, Darmstadt
Mass measurements of short-lived exotic nuclei can be performed using Isochronous Mass Spectrometry at the FRS-ESR facility at GSI. The mass values are obtained from the revolution time measurements using a time-of-flight detector. Ions passing the detector release secondary electrons from a thin carbon foil which are guided to micro channel plate (MCP) detectors by electric and magnetic fields. The time accuracy as well as the rate capability of the TOF detector are crucial parameters for the performance of IMS. Simulations showed that by increasing the kinetic transport energy of the secondary electrons from the foil to the MCPs the time accuracy of the detector can be improved. In measurements with a modified detector with higher kinetic transport energies the timing performance of the detector was improved by 50%. Additionally MCPs with a smaller pore size to improve the rate capability and a thinner carbon foil to reduce the energy loss in the foil were installed in the TOF detector. In an online experiment with uranium fission fragments a 10 times higher turn number of the ions could be observed than in former experiments.